NASA Phoenix Mission Ready For Mars Landing 101
Several readers relayed the press release from JPL about the upcoming landing of NASA's Phoenix Mars Lander on May 25. It's going to set down in the north polar regions and look for indications of whether conditions have ever been favorable for microbial life. "Phoenix will enter the top of the Martian atmosphere at almost 21,000 kilometers per hour... In seven minutes, the spacecraft must complete a challenging sequence of events to slow to about 8 kilometers per hour... before its three legs reach the ground. Confirmation of the landing could come as early as 7:53 p.m. EDT. 'This is not a trip to grandma's house. Putting a spacecraft safely on Mars is hard and risky,' said Ed Weiler, associate administrator for NASA's Science Mission Directorate. 'Internationally, fewer than half the attempts have succeeded.'"
Great stuff I guess but why isn't NASA doing more? (Score:0, Insightful)
It just seems like a way to earn a good salary and have a lot of fun!
Re: Hard and Risky??? (Score:3, Insightful)
I work in a factory, and the first time that someone uses something like a table saw, they are nervous. I is a dangerous tool and could seriously injure them if they are not careful. But most of the injuries I see cause by power tools are by people who have gotten too comfortable with them and have forgotten about the risk involved.
commonplace != safe and easy
Re: Hard and Risky??? (Score:5, Insightful)
Cut them some slack! Most of us slashdot readers have trouble getting an Apache install right the first time through. These guys are doing nearly the impossible and they don't get much of a chance to fix any mistakes.
There are like THOUSANDS of possible things that could go wrong with the landing that DON'T because the engineers did their job. If you have ever engineered anything, you know how much you have to think ahead. They sat really hard and long and tried to perfect the landing process.
But it's darned hard. Mars is really really really far away. The data transfer speed to the lander is like 16KB/s on a good day. You can't send realtime flight data and have a pilot fly the thing with a joystick (because of the latency and the bandwidth is just too limited). You just have to build smart control logic into the thing and hope for the best.
And -- what can ruin the whole thins is -- just one largish rock in the wrong place and the whole mission is a failure. Historically, only 5 out of 13 landers made it to the surface operational!
So, stop being a douche and start appreciating how hard this all is. And it isn't just NASA -- the Brits also tried and failed. It's hard. NASA is doing a great job. Let's see you send 100LBS of spacecraft millions of miles away and have it get there safely. It's pretty amazing it ever worked at all!
Oh and what "corporate committes"? Last I checked NASA was a government agency.
Stop thinking like a corporate douch and start thinking like a scientist. These guys are smarter than you or I and give them some respect.
Re: Hard and Risky??? (Score:2, Insightful)
In short, scientists study, but all engineers are very comfortable with the idea of managed risk. It is part of nearly every design that is built. Yes, mistakes do occur from time to time, but I continue to see on every mission they do people jumping up and down whenever their craft successfully lands. The first couple of times they do this it is understandable, but after a couple of times you really have to start wondering if they are not designing their systems by looking at all the things that could go wrong, but rather just with the number of things they need to get it to get right...
Re: Hard and Risky??? (Score:2, Insightful)
Meaning, no job is just accepted to be risky by nature, because there really is no reason for it. As OSHA has shown time and time again, safety is always built on the procedures put in place that you follow every-time. It is these procedures that keep people safe. It is only when people get lazy, and stop following the procedures that they get hurt...
Re:Slow to about 8 kilometers per hour. (Score:1, Insightful)
8 km/h is the target touchdown velocity. They'll come pretty close, probably with a couple km/h of that speed, but it probably won't be exactly that. 16 km/h might even be survivable. The point is 25,000 km/h, or even 100 km/h is not survivable.
But there's a whole lot of steps before that:
* Navigation - Mars Climate Orbiter missed orbit by a fraction of degree. It failed. Coming in too steep would also mean failure.
* Entry - at 25,000 km/h, the spacecraft is toast if its protection fails.
* Heat shield separation - If this doesn't happen, the guidance system can't operate.
* Reaction control system - Keeps the lander stable in flight. Tumbling would tear it apart.
* Parachute deployment - Obvious
* Parachute release - If it fouls the probe, it can't deploy its solar panels
* Retrorocket - Has to coordinate with guidance and RCS to slow to touchdown speed and stay in the right orientation. Has to fire on demand. Can't explode.
* Leg Deployment - All must deploy for a stable touchdown. The leg deployment on Mars Polar Lander jarred the touchdown sensor, causing the engines to shut down before touchdown. Mission failed.
* Engine cutoff - Has to happen just a few feet above the ground to avoid damaging the lander with backblast and debris.
* Touchdown - Legs are partially collapsible to cushion the landing.
If the speed is right, and it misses any large rocks, and the parachute doesn't drift down on top of it, and all the other things above go right, at this point EDL was successful. After being shaken and hurled into space onboard a rocket, drifting dormant in the cold for 8 months, plumetting through the atmosphere at outside temperatures that would melt the lander itself, bouncing at parachute opening, facing the harsh wind at heat-shield separation, and freefalling several feet to the ground, now the hope is the delicate motors, joints, and electronics on the probe still work.
The more you know about what could go wrong, the more you wish EDL was over already.
half as many (Score:3, Insightful)